Type bar trip mechanism



Aug. 4, 1959 R. D. DODGE TYPE BAR TRIP MECHANISM 2 Sheets-Sheet 1 Filed Nov. 12, 1957 FlGv.1

FIG.3

IN VEN TOR. RONALD D. DODGE ATTORNEY g- 4, 1959 R. D. DODGE 2,897,941

TYPE BAR TRIP MECHANISM Filed Nov. 12, 1957 2 Sheets-Sheet 2 United States Patent TYPE BAR TRIP MECHANISM Ronald D. Dodge, Lexington, Ky., assignor to International Business Machines Corporation, New York, N .Y., a corporation of New York Application November 12, 1957, Serial No. 695,949

7 Claims. (Cl. 197-17) This invention relates to typewriters and more particularly to an improved tripping mechanism and cam con .trol for a power driven type bar drive. a

In conventional power driventype bar mechanisms, examples of which are shown in US. Letters Patent 2,723,740 and 2,796,966, a cam is held normally out of engagement from a continuously driven power source, such as a power roller, and is pushed into engagement with the power roll to initiate a type bar print stroke.

One of the primary objects of power typewriters is to reduce the effort exerted by the operator and thereby reduce fatigue. It is desirable to require a very light touch on the keys to initiate a type bar operation. The conventional operating cam must be of sturdy construction and, of course, has weight and inertia which must be overcome to initiate a type bar stroke.

One object of this invention is to provide an improved tripping mechanism for a power driven type bar drive. A further object of this invention is to provide an improved tripping mechanism for a power driven type bar requiring less tripping force than the conventional trip mechanisms.

A still further object of this invention is to provide a type bar tripping mechanism having a light weight member manually actuated to thereafter effect a power driven engagement of the usual type bar actuating cam with the power roller.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

Briefly, this invention relates to an improved power driven type bar cam control and tripping mechanism therefor, wherein a relatively light weight pilot cam is manually engaged with a power roller and is driven thereby to drive the usual operating cam into engagement with the power roller rather than to manually push the heavier operating cam into engagement with the power roll.

In the drawings, Figs. 1, 2 and 3 are side elevations showing the typebar drive mechanism at various stages of operation.

The type bar mechanism illustrated in the drawings comprises a key lever pivotally mounted on a rod 12, a cam lever 14 pivotally mounted on a rod 16, a pilot cam 18 and an actuating cam 20 both pivotally mounted on a pin 22 carried by the cam lever 14, a continuously driven power roll 24 and a type bar 26 pivotally mounted on a rod 28 and connected by a link 30 to the cam lever 14. The type bar normally rests on a pad 32 and, when actuated, is thrown against a platen 34 shown in Fig. 2.

The key lever 10 normally is biased to a raised position by a spring 36 and is movable to an actuated position shown in Fig. 2. The key lever 10 carries a finger 38 which is adapted to engage a lug 39 on an actuating plate 40 pivotally and slidably mounted by a slot 42 on a pin 44 carried by the cam lever 14. The actuating plate 40 is biased to the left by a spring 46 attached to 8. lug 48 on the cam lever 14. A lug 50 on the actuating plate 40 rests on the upper end of the pilot cam 18 whereas the lower end of the pilot cam 18 rests closely adjacent the power roll 24. The pilot cam 18 is biased counterclockwise by a spring 52 attached to a finger 54 on the actuating cam 20. The cam 20 is biased counterclockwise by a spring 56 connected to a finger 58 carried. by the cam lever 14 and is limited in counterclockwise movement by a lug 60 hearing against the cam lever 14.

When the key lever 10 is moved to the dotted position of Fig. l, the finger 38 hearing on the lug 39 pivots the actuating plate 40 counterclockwise about the pin 44 whereby the lug 50 bearing against the pilot cam 18 pivots the latter clockwise about the pin 22 moving the lower end of the pilot cam into engagement with the power roll 24. The pilot cam has little weight and is freely rotatable on the pin 22 and, due to the light weight and the mechanical advantage gained by the various lever arms of the system, very little force is required to bring the pilot cam into engagement with the power roll.

When the power roll engages the pilot cam it continues the clockwise rotation of the pilot cam which engages a stud 62 formed on the actuating cam 20 and drives the cam 20 in a clockwise direction about the pin 22.

This clockwise movement brings the cam 20 into engagement with the power roll 24 and, due to the contour of the cam 20, drives the cam lever 14 clockwise, about its pivot 16, thereby, through the link 30, driving the type bar 26 against the platen 34. As the cam lever swings clockwise, the cam 20 moves away from the power roll and the cam lever and the type bar continue in free flight while the cam 20 is restored to its normal position, relative to the cam lever, by its spring 56, and the pilot cam 18 is restored to its normal position, relative to the cam 20, by its spring 52. Upon completion of the type bar stroke, the cam lever 14 is restored to its normal position by a spring 64 connected to a bracket 66 on the machine frame.

When the cam lever 14 is rocked counterclockwise by the spring 64 at the end of the type bar stroke, it is desirable to prevent a repeat type bar stroke if the key 10 is still in the actuated position. As the cam lever swings counterclockwise, the lug 39 on the actuating plate engages the right hand edge of the finger 38 on the key lever 10 causing the plate 40 to slide on the pin and slot connection to the position shown in Fig. 3. All the parts except the actuating plate 40 are in their normal inactive positions corresponding to the full line positions of Fig. 1.

When the key lever 10 is released and is returned to its normal position by the spring 36, the finger 38 is retracted and the actuating plate 40 is free to move to the left, under tension of the spring 46, to the normal full-line position of Fig. 1.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. An improved type bar drive mechanism for a typewriter having a power driven roller comprising, a cam lever with an associated type bar, means mounting said cam lever and said type bar for movement from a rest position to a print position, a manipulatable key lever, and means responsive to manipulation of said key lever for initiating a type bar print stroke comprising, a pilot,

cam, an actuating cam, means pivotally supporting said cams on said cam lever for selective engagement with said power roller, means operable by said key lever for engaging said pilot cam with said power roller, and means operative to drivingly connect said pilot cam and said actuating cam when said pilot cam is engaged with said power roller for moving said actuating cam into engagement with said power roller whereby said cam lever and said type bar are moved to said print position.

2. An improved type bar drive mechanism for a typewriter having a power driven roller comprising, a cam lever with an associated type bar, means mounting said cam lever and said type bar for movement from a rest position to a print position, a manipulatable key lever, and means responsive to manipulation of said key lever for initiating a type bar'print stroke comprising, a pilot cam, an actuating cam, means pivotally supporting said cams on said cam lever for selective engagement with said power roller, means operable by said key lever for moving said pilot cam into engagement with said power roller, means operative to drivingly connect said pilot cam and said actuating cam when said pilot cam is engaged with said power roller for moving said actuating cam into engagement with said power roller whereby said cam lever and said type bar are moved to said print position, and means operative to block a second engagement of said cams with said power roller when said key lever is held in its manipulated position.

3. An improved type bar drive mechanism for a typewriter having a power driven roller comprising, a cam lever with an associated type bar, means mounting said cam lever and said type bar for movement from a rest position to a print position, a key lever, and means responsive to manipulation of said key lever for initiating a type bar print stroke comprising a pilot cam, an actuat ing cam, means pivotally supporting said cams on said cam lever for selective engagement with said power roller, means resiliently restraining said pilot cam from engagement with said power roller, means resiliently restraining said actuating cam from engagement with said power roller, means resiliently holding said cam lever and said type bar in said rest position, means biasing said key lever to an inoperative position, means operable by said key lever for overcoming said pilot cam restraining means and moving said pilot cam into engagement with said power roller, and engaging means drivingly connecting said pilot cam and said actuating cam when said pilot cam is engaged with said power roller for overcoming said actuating cam restraining means and moving said actuating cam into engagement with said power roller whereby said cam lever and said type bar are moved against the force of said cam lever and type bar restraining means to said print position 4. The device of claim 3 having means operative to block a repeat engagement of said cams with said power roller when said key lever is held in its manipulated position.

5. An improved type bar drive mechanism for a typewriter having a power driven roller comprising, a cam lever with an associated type bar mounted for movement from a rest position to a print position and spring biased to said rest position, a key lever, and means responsive to manipulation of said key lever for initiating a type bar print stroke comprising, a pilot cam spring biased from engagement with said power roller, an actuating cam spring biased from engagement with said power roller, means pivotally supporting said cams on said cam lever; for selective engagement with said power roller, means operable by said key lever for moving said pilot cam into engagement with said power roller, means operative to drivingly connect said pilot cam and said actuating cam when said pilot cam is engaged with said power roller for moving said actuating cam into engagement with said power roller whereby said cam lever and said type bar are moved to said print position.

6. The device of claim 5 having means operative to block a repeat engagement of said cams with said power roller when said key lever is held in a manipulated position.

7. The device of claim 6 wherein the last said means comprises an interposer carried by said cam lever and normally interposed between said key lever and said pilot cam for transmitting actuating movement of said key lever to said pilot cam, means mounting said interposer for pivotal and sliding movement on said cam lever, and latch means operative at the end of said print stroke to latch said interposer in an inoperative position relative to said key lever and said pilot cam as long as said key lever is held in said manipulated position.

No references cited. 

